1. Field of the Invention
This invention relates to an apparatus and a method for manufacturing a magnetic disc used in a high-density and large-capacity recording device.
2. Description of Related Art
In general, a magnetic disc for a recording device comprises a mirror-polished disc base plate of non-magnetic material, and a magnetic recording layer which is formed on the disc base plate by a sputtering method, a deposition method or the like. When such a magnetic disc is used in a magnetic recording device adopting a CSS (Constant Start and Stop) system, the magnetic disc and a magnetic head are kept in contact with each other at the contact surfaces thereof at a non-operation time while they are slid in contact with each other at an operation start time and an operation stop time. Therefore, the contact surface of the magnetic disc suffers abrasion. In order to overcome this disadvantage, a protection film which comprises a thin film of carbon, ceramics or the like is formed on the magnetic recording layer of the magnetic disc by a sputtering method or the like, then the disc surface is subjected to a polishing treatment to lower the flying height of the magnetic head, and then a lubricant film is formed on the polished disc surface to suppress abrasion between the magnetic head and the surface of the magnetic disc and improve the durability of the magnetic disc.
Generally, the polishing treatment on the magnetic disc surface after formation of the protection film as described above is carried out as follows. That is, a polishing tape is formed by adhesively fixing abrasive particles onto a tape, and it is pressed against the surface of the rotating magnetic disc by a press roller, air pressure or the like. Further, the lubricant film is formed by a batch process in which plural magnetic discs are collectively immersed in lubricant solution for a predetermined time, and then gradually drawn out.
In the formation of the lubricant film, a curing treatment must be conducted on the lubricant in accordance with the used lubricant or based on a required performance therefor. In this case, a batch process in which plural magnetic discs provided with lubricant are collectively inserted into a heating device and heated for a predetermined time is carried out.
Here, if the lubricant amount on the disc surface is small, sufficient durability cannot be obtained for the magnetic head and the magnetic disc. On the other hand, if the lubricant amount is excessive, an adsorption phenomenon between the magnetic head and the magnetic disc occurs, and damage of the magnetic disc and the magnetic head results, and failure of disc rotation. Accordingly, adjustment in the lubricant amount and the curing treatment is required to be carried out with extremely high precision.
However, in the conventional method as described above, the heating temperature for the curing process is dispersed in the heating device, that is, there occurs a temperature distribution in the heating device in the curing process, so that any dispersion occurs in products. Further, after the curing process, a large number of discs must be stocked to wait for the next process, and thus its yield is low. Still further, there is a possibility that several hundred defective products are simultaneously obtained because of a failure in the curing treatment device, a workers mistake or the like.
A magnetic disc of higher density and larger capacity has been recently required, and the precision of the magnetic disc surface and a lubricant performance have been also required to be improved. In order to satisfy this requirement, a control method for a lubricant supply device and a curing treatment device has been proposed. Such a control method causes various problems, for example, that a more complicated control operation is required, the device price is increased, and productivity of discs is lowered. However, these problems cannot be solved by the conventional batch type of manufacturing apparatus as described above.